From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [PATCH 0/4] Fiemap, an extent mapping ioctl - round 2 Date: Wed, 2 Jul 2008 15:28:54 +0100 Message-ID: <20080702142854.GB2993@shareable.org> References: <20080625221835.GQ28100@wotan.suse.de> <4863A1C5.7020403@redhat.com> <20080627014119.GW29319@disturbed> <20080627094156.GA30200@shareable.org> <20080627224843.GZ6239@webber.adilger.int> <4865BC50.2030804@redhat.com> <20080702062612.GP6239@webber.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , Mark Fasheh , linux-fsdevel@vger.kernel.org, Andreas Dilger , Kalpak Shah , Josef Bacik To: Andreas Dilger Return-path: Received: from mail2.shareable.org ([80.68.89.115]:49034 "EHLO mail2.shareable.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752955AbYGBO24 (ORCPT ); Wed, 2 Jul 2008 10:28:56 -0400 Content-Disposition: inline In-Reply-To: <20080702062612.GP6239@webber.adilger.int> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Andreas Dilger wrote: > On Jun 27, 2008 23:21 -0500, Eric Sandeen wrote: > > even w/ metadata out of the way the ext4 extent format is still > > capped at 128M per extent right, even if they're contiguous. Which led > > me to the little though experiment about hm, is this 1G file 1 extent or > > 8 and what should fiemap return... > > The current FIEMAP code will return 8 extents, which mirrors the number > of physical extents on disk. This could be important to the person > looking at the file, as it will be clear that there are too many > extents to fit into the inode and the extent tree will include an index > block. > > I was a bit on the fence about this, but I agree with David that if > userspace has more information (e.g. all of the on-disk extent data) > it can always merge it, but it can't "un-merge" the data returned > from the kernel. Ok, wouldn't be appropriate to include the extent of the index block as well, somewhere, so that userspace can see which parts of the disk must be read to read the file? (As you say, more information...) -- Jamie